Abstract
Atlantic bluefin tuna (Thunnus thynnus; BFT) abundance was depleted in the late 20th and early 21st century due to overfishing. Historical catch records further indicate that the abundance of BFT in the Mediterranean has been fluctuating since at least the 16th century. Here we build upon previous work on ancient DNA of BFT in the Mediterranean by comparing contemporary (2009–2012) specimens with archival (1911–1926) and archaeological (2nd century BCE–15th century CE) specimens that represent population states prior to these two major periods of exploitation, respectively. We successfully genotyped and analysed 259 contemporary and 123 historical (91 archival and 32 archaeological) specimens at 92 SNP loci that were selected for their ability to differentiate contemporary populations or their association with core biological functions. We found no evidence of genetic bottlenecks, inbreeding or population restructuring between temporal sample groups that might explain what has driven catch fluctuations since the 16th century. We also detected a putative adaptive response, involving the cytoskeletal protein synemin which may be related to muscle stress. However, these results require further investigation with more extensive genome-wide data to rule out demographic changes due to overfishing, and other natural and anthropogenic factors, in addition to elucidating the adaptive drivers related to these.
Highlights
Overfishing has reduced numerous fish populations to remnants of their historical levels[1,2], yet we have a poor understanding of what impact this has had on their evolutionary potential and r esilience[3]
Locus SNP41 was identified as a putative adaptive response after being detected as an outlier between pooled contemporary and historical groups
We found no evidence of genetic diversity loss or population restructuring in contemporary BFT sample groups of the eastern Atlantic and Mediterranean compared with those from the early 20th century CE prior to spawning biomass depletion and species range contraction[22,25], and the 4th–15th century CE prior to a significant period of intense trap fishing marked by fluctuating c atches[26,27]
Summary
Overfishing has reduced numerous fish populations to remnants of their historical levels[1,2], yet we have a poor understanding of what impact this has had on their evolutionary potential and r esilience[3]. This information is crucial to predict future demographic changes and promote sustainable fisheries m anagement[4,5]. The current study investigates genetic variability in eastern Atlantic and Mediterranean BFT prior to both their 21st century population collapse, and record trap catches in the 16th and 18th century, using archived early20th century specimens, and archaeological remains, respectively. A recent whole genome sequencing (WGS) study[42], that did not detect genetic erosion or adaptive responses in two Atlantic cod populations following 20th century overfishing, may indicate, that the latter is the case for some populations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
